The proposed work deals with the function and biosynthesis of both cytoplasmic and outer membrane proteins of Escherichia coli. With respect to cytoplasmic membrane proteins, an attempt will be made to isolate amber mutants in the structural genes of the three polypeptides of nitrate reductase, and to use a ts suppressor to study the regulation of this enzyme. Studies will be continued on the regulation of this enzyme by oxygen, and on the turnover of the various enzyme subunits. Lipid-protein interactions will also be investigated. With respect to the outer membrane proteins, studies are planned on the post-translational modification of lysine residues of protein 1, on the isolation of mutants of phage PA-2 unable to carry out the lysogenic conversion leading to the production of protein 2, and on the identification of the structural gene for protein 1. We plan to initiate a study on the killing action of complement, using antibody directed against the phage lambda receptor, since we can modulate the amount of this protein antigen in the outer membrane by genetic means. BIBLIOGRAPHIC REFERENCES: MacGregor, C.H., Regulation and assembly of nitrate reductase from E. coli. In Microbiology 1977 (D. Schlessinger, ed.) American Society for Microbiology, Washington, D.C. in press. MacGregor, C.H., and A. Christopher. Asymmetric distribution of nitrate reductase subunits in the cytoplasmic membrane of E. coli: Evidence derived from surface labeling studies with transglutaminase. Biochemistry, submitted, Jan. 20, 1977.